Field of Invention
The present invention relates to a thermal pile sensing structure integrated with one or more capacitors; particularly, it relates to such a thermal pile sensing structure which is integrated with a MIM capacitor or a PIP capacitor, to reduce the chip area and noise.
Description of Related Art
Please refer to FIG. 1 in conjugation with FIG. 2. FIG. 1 shows a block diagram of a conventional thermal pile sensing structure which is applied in a temperature sensing module. FIG. 2 shows a cross section view of the conventional thermal pile sensing structure. The conventional temperature sensing module 100 comprises the conventional thermal pile sensing structure 10, a noise filter 81, a noise filter 82, a differential amplifier Amp, an analog-to-digital convertor ADC and a temperature sensor 80. The thermal pile sensing structure 10 is capable of generating a voltage difference signal VDS according to a temperature difference, whereby the temperature sensing module 100 can sense temperature. The voltage difference signal VDS (which is a differential signal) generated by the thermal pile sensing structure 10 is processed by the noise filter 81 and the noise filter 82, and inputted to the differential amplifier Amp. The output (which is also a differential signal) of the differential amplifier Amp is inputted to the analog-to-digital convertor ADC. The analog-to-digital convertor ADC also receives a temperature signal TS outputted from the temperature sensor 80. The noise filter 81 and the noise filter 82 includes a capacitor C1 and a capacitor C2, respectively. Besides, the conventional temperature sensing module 100 further comprises a capacitor C3. In this prior art, the capacitor C1, the capacitor C2 and the thermal pile sensing structure 10 are three independent components, which are packaged separately.
Please refer to FIG. 2. The conventional thermal pile sensing structure 10 comprises: a substrate 11; an infrared sensing unit 16; and a partition structure 15. The infrared sensing unit 16 is formed on the substrate 11. The infrared sensing unit includes a first sensing structure 161 and a second sensing structure 162, wherein a hot junction H is formed between the first sensing structure 161 and the second sensing structure 162 at a location where the first sensing structure 161 and the second sensing structure 162 are close to each other. The partition structure 15 surrounds the infrared sensing unit 16. A cold junction C is formed between the partition structure 15 and the first sensing structure 161 at a location where the partition structure 15 and the first sensing structure 161 are close to each other and another cold junction C is formed between the partition structure 15 and the second sensing structure 162 at a location where the partition structure 15 and the second sensing structure 162 are close to each other. The temperature difference between the hot junction H and the cold junction C generates the voltage difference signal VDS. In order for the infrared sensing unit 16 to sense the signal more accurately, this prior art further includes a light filter layer 14, which is connected to the thermal pile sensing structure 10 via a bonding layer 13.
If the thermal pile sensing structure 10 is manufactured by a CMOS manufacturing process, the partition structure 15 usually includes a polysilicon layer Poly 1, plural metal layers M1-M4 (shown to be four layers in FIG. 2, but the number of the layers is not necessarily four) and plural via layers V. The first sensing structure 161 and the second sensing structure 162 are made of the metal layer M1 and the polysilicon layer Poly 1. Dielectric layers 12 provide insulation between the electrically conductive structures. The voltage difference signal VDS is transmitted through a transistor circuit 17.
In this prior art, as mentioned-above, the capacitor C1 and the capacitor C2 are provided between the thermal pile sensing structure 10 and the electrical circuit, to filter noises. The capacitor C1, the capacitor C2 and the thermal pile sensing structure 10 are three independent components, which are packaged separately. Hence, this prior art is disadvantageous in that: the overall size of the module is larger, and the manufacturing cost is high.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes a thermal pile sensing structure integrated with a MIM capacitor a PIP capacitor, which reduces the chip area and also reduces the noise.